When this year's Reading and Leeds festival lineup was announced at an industry party last night, you may have heard the distinct sound of rockers spluttering into their beer. For the infamously hard-rockin' festival boasts the least "rock" lineup ever. None of the headliners – Arctic Monkeys, Radiohead and Kings of Leon – are known for their riffing or tattoos. Slightly further down the bill, you'd be struggling to find a convincing, balls-out rock band amid the likes of Bloc Party (second on the bill for two consecutive years), Glasvegas, Vampire Weekend and Kaiser Chiefs.

Granted, the world's oldest surviving pop festival has been through one or two phases since it began as the National Jazz festival in Richmond in 1961. But since the 1971 shift to Reading, it has always been primarily a rock festival. For most of the 70s, it was synonymous with progressive rock, and singers dressed as flowers.

The dalliance with punk during 1978's festival was a bold experiment that led to battles between fans. The Ramones – who appealed to punks and rockers, not least because of their genre-bending uniform of rock barnets and leather jackets – still featured on the bill the following year. But in the 80s, Reading became known for acts like Alice Cooper, Marillion and, er, Status Quo, while occasionally being able to shoehorn a rockish act like the Mission on to the bill.

However, rock's slight slump in popularity in the late 80s led to the infamous and disastrous attempt to take the festival in a more commercial, AOR direction. Thus, in 1988 – the year of acid house – Reading rocked (albeit softly) to the ghastly sound of poodle-permed Starship, followed by Meat Loaf and Bonnie Tyler. Meat was greeted with a hail of bottles, while Ms Tyler probably had a Total Eclipse of the Heart when she realised they contained urine.

Since then (and especially when it acquired a second site at Leeds) the festival has settled into being rock-oriented. Nirvana headlined in 1992, when Kurt Cobain was famously pushed onstage in a wheelchair by Guardian music blog contributor Everett True. There's always been a lot of indie (Pulp and the Stone Roses) and a bit of rap (Ice Cube, the Beastie Boys) – but at least one whole day has always been dominated by bands with loud guitars and metal piercings. As recently as 2002, rock acts featured on every single day, whether they were the Sick of it All, Jane's Addiction, Cave-In or Reel Big Fish. The rock day in Leeds was a total noise fest – Slipknot and the Offspring topped off by a rare sighting of Guns N' Roses – although a minor riot prompted a subsequent change of site.

In the last three years, Reading and Leeds has still hosted rock monoliths from the Red Hot Chili Peppers and Metallica to Nine Inch Nails and Rage Against the Machine. Which makes this year's bill suddenly look very different. You have to examine the lineup closely to see metal acts such as Funeral for a Friend and the Deftones, all of them buried down the bill. You can't help wonder if some bod booked the Eagles of Death Metal to pacify the purists – until someone pointed out that actually they weren't death metal. Or the Eagles.

Meanwhile, all the bigger rock acts seem to have been booked by Download. So has Reading and Leeds lost out, or made a calculated decision to realign itself with indie? Or has the festival simply forgotten how to rock?